Keys or buttons may be found in various areas of technology, e.g. computers, automobiles, musical instruments and many more. In particular, they are an integral component of keyboard instruments, such as the piano and the keyboard. But also modern electronic musical instruments have keys, which can, for instance, be arranged in a matrix with rows and columns (i.e., 8×8, 8×4 and so on). Analogously to the piano, the impact dynamics of the key (i.e., the velocity of the downward push) and hence the pressure applied physically to the key are detected electronically using sensor technology and analyzed electronically. The information gathered from impact velocity and pressure serves as the basis to infer the volume of the sound generated by the key pressed. However, apart from volume regulation, electronic instruments and music controllers, resp., comprising such technology, offer only limited means to formulate and manipulate, resp., the sound beyond the volume.
Ever since the conception of electronic musical instruments, it has become desirable to emulate and reproduce sound-wise, resp., other analogue instruments (e.g. string and wind instruments). Hence, there is the wish to capture, measure and ultimately to simulate the facilities of expression which are available to a musician playing analogue instruments (such as vibrato, timbre, tremolo, variations in tone and volume etc.) in electronic musical instruments. To accommodate for this wish, many electronic key-based musical instruments and controllers, resp., have additional means to manipulate and control, resp., the sound. Among these are the above-mentioned possibility to measure and analyze, resp., the keystroke upon impact, and further additional mechanisms, such as the sustain pedal, pitch bend wheel or the modulation wheel. However, not only must these additional mechanisms be used separately from the played key or button, but what is more, they only allow for the same effect to be applied to all keys—hence the particular sounds created with the keys cannot be modulated individually and thus a parallel play of several keys with different expression effects (polyphone) is not possible.
Electronic musical instruments and software-based musical instruments, resp., with their sound libraries offer a plethora of expressive sounds. To be able to control and play, resp., these sounds multi-dimensionally, i.e. corresponding to the position of, e.g., the key-striking user's finger, a sensor technology for the instrument keys and pads, resp., is needed, which can, on the one hand, analyze the finger position electronically in X-Y direction and, on the other hand, the force applied to the key an the pad, resp., by the finger in Z direction. A further important information is the detection of movements in the X-Y plane that go beyond the key/pad borders. In relation to a Cartesian coordinate system “Z direction” refers to the direction in which the—vertical—downward movement of the key or button occurs, while “X” and “Y direction” establish the orthogonal—horizontal—plain in which, e.g., the key's surface is located.
Generally, the sensors currently known to detect the force applied to the key in Z direction are FSR sensors (force sensing resistor), as disclosed, e.g., in U.S. Pat. No. 6,909,354 B2 of Interlink Electronics, Inc. An FSR is a contact sensor, which creates an electrical resistance between two electrodes in case of contact. Such sensors have certain disadvantages, e.g., a high entry threshold, a behavior that is hard to reproduce around this entry threshold and a high effort (i.e., several FSR sensor planes) to detect the X and Y dimensions simultaneously to the Z dimension.
A further disadvantage of known keys—particularly those having sensors—is the non-existent or only very limited illumination. This is due to the fact that keys or buttons with sensors must be transparent or must have breaks to guide the light if they are to be illuminated on their surface. This makes designing such keys highly problematic. An illumination, however, is in many instances desirable for the use in modern electronic musical instruments. E.g., the illumination of a just played musical note and key, resp., or the key's status can be indicated or other optical signals can be made possible.
Hence, there is still a need for a key or button and touchpad, resp., which detects not only the force (i.e., pressure) applied in Z direction, but also the position in X-Y direction of, for instance, a user's finger pressing the key. Moreover, there is still a need for a key that is sufficiently illuminated.